Controller for electric generators.



R. A. HOPPE & T. L. LEE.

CONTROLLER FOR ELECTRlC GENERATORS.

APPLICATION FILED NOV=17.1913.

1,149,054. Patentedmlg. 3, 19 15.

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ROBERT A. HOPPE AND THOMAS L. LEE, OF ROCHESTER,

NEW YORK, ASSIGNORS 'TO NORTH EAST ELECTRIC COMPANY, OF ROCHESTER, NEWYORK, A CORPORATION OF NEW YORK.

To all whom it may concern Be it known that we, ROBERT A. Horn: andTHOMAS L. LEE, citizens of the United States, and residents ofRochester, in the county of Monroe and State of New York, have inventedcertain new and useful Improvements in Controllers for ElectricGenerators, of which the following is a specification.

This invention relates to an electro-magnetic instrument, in the natureof a relay, for the automatic control of an electric generator operatingunder variable speed and load, particularly in connection with astorage-battery.

In an electric system, such as is employed on railway trains andmotor-vehicles, in.

which the generator is driven at variable speed by connection with apart of the mechanism of the vehicle, it is common to employ a devicewhich prevents undue rise in the electromotive force of the generator,at high speeds, by automatically introducing resistance into the circuitthrough which the shunt field-winding of the generator is energized,such a device being usually in the form of a* simple electro-magneticrelay, having an armature controlling a short-circuit around aresistance-device. In such an instrument the armature tends to have avibratory or chattering action when the generator is at a criticalspeed, with a more or less destructive action upon the contact-devicescontrolled by the armature.

One object of the present invention, accordingly, is to improve aninstrument of the kind in question by damping this vibratory action, andto this end we propose to emplov a highly conductive annular member,surrounding-the magnetic .core of the instrument and affording a pathfor eddycurrents, by which the magnetic flux in the a core is caused tolag.

For the further protection of the contactdevices we employ simple andefi'ective' means for conducting from them the heat resulting fromsparking.

To further improve and Simplify the instrument, we propose to employ theannular conductive member above referred to as a' means for conductingheat away from the resistance-Wire with which the instrument cooperates,and to this end we make the conductive memberin the form of a spool,upon which the resistance-mm is wound, the

Specification of Letters Patent.

CONTROLLER FOR ELECTRIC GENERATORS.

Patented Aug. 3, 1915.

Application filed November 17, 1913. Serial No. 801,507.

winding being preferably noninductive in arrangement, so as not tomodify the action of the core upon the armature.

In systems of the kind in question, where in a storage-battery is used,it is also com mon to employ a device, in the nature of a relay, bywhich the return-flow of current from the battery through the generatoris normally prevented, when the speed of the generator falls so low thatthe electromotive force generated is less than that of the battery.

A further object of the present'invention is to combine this latterinstrument, which will be hereinafter referred to as a masterrelay, withthe instrument above referred to, which will be hereinafter described asa limiting-relay, in such a manner as to produce a simple, compact andinexpensive useful cooperation between the two armatures, by which theiroperation is rendered more certain.

To this end we employ an instrument in which the two armaturesconstitute parts of a single magnetic circuit, having two air gaps butonly a single set of windings, these windings preferably comprising. aconstantly-energiz'ed shunt-winding, and a se-' Ties-winding controlledby the master-relay armature.

In the accompanying drawings Figure '1 isa front-elevation of acontroller embodying the present invention; Fig. 2 is a righthandelevation of the same; Fig. 3 is a vertical section on the line'33 inFig. 2; and Fig. 4 is a diagram, showing the preferred .manner ofconnecting the controller with the other parts of the generating-system.

The invention is illustrated as embodied .in an instrument adapted tocooperate with a differentially-wound electric generator connected withtranslating-devices and with a storage-battery floated on the line.

As shown particularly in Fig. 3, the controller; comprises a straightcore 5 of soft iron," which is supported, at its ends, by plates 6 ofnon-magnetic material such as brass. These plates, in turn, are fixed toa base-plate 7 of iron.

The two armatures, 8 and 9, of th'e controller are mounted upon pivots10 and 11 'bers 12 and 13, we employ damped, is in in the oppositeforked ends of the base-plate 7 in position to cooperate with theopposite endsof the core 5. The armature 8, which is proper to theaction of the instrument as a limiting-relay, carries a contactmember 12which cooperates with a fixed contact-member 13 mounted upon a plate 14:of insulating-material, this plate being fixed to the end-plates 6, asshown in Fig. 3, and

one of the attaching-devices 15 being con veniently employed also as oneof the binding-posts for connecting the instrument with externalcircuits. A spring 16, connecting the lower end of the armature 8 withthe base-plate 7, tends to draw the armature 8 away from the core 5, soas to maintain the contact-devices 12 and 13 in engagement, and this isthe position occupied by the parts except when the generator exceeds apredetermined speed, to which the spring 16 is regulated. Y

The armature 9, which is proper to the operation of the instrument as amasterrelay or reverse-current cut-out, carries a contact-member 17whichcooperates with a similar member 18 mounted upon theinsulating-plate 14. A spring 19, connected with the lower end of thearmature 9, tends to move the armature away from the core 5, and todisengage the contacts 17 and 18, and this outward movement of thearmature is limited by a stop-arm 20 (Fig. 1), fixed be-. tween theleft-hand plate 6 and the corresponding end of the core, as shown inFig. 3. Two windings are employed to energize the magnetic circuit ofthe controller. These windings are mounted upon the core 5; and theinner winding 21, which may be described as the series-winding,comprises a few turns of heavy wire, while the outer winding 22, whichmay be described as the shunt-winding, comprises many turns of finewire. Asa simple and effective device for conducting heat away from thecontact-mema thin plate 23 of material, such as copper, having a highheat-conductivity, this plate being secured in place by thecontact-member 12, which is in the form of a rivet passing through theplate 23 and the armature 8 and headed on both sides to fix it in place.The plate 23 is further provided with lugs 2 L embracing the lateraledges of the armature to prevent it from rotating about thecontact-member 12. Heat resulting from sparks or arcing between thecontact-members is conducted directly to the plate 23, from which it escapes by conduction and convection, and in this manner the wear uponthe contactmembers is substantially reduced.

The annular conductive member by which the movements of the armature 8are the form of a spool 25 of copper, which is fitted upon theright-hand end of the core 5, as shown in'Fig. 3; and in order that thismember may serve the further purpose above referred to, of conwindingmaybe non-inductive it is preferably wound in opposite directions fromits middle point, as shown diagrammatically in Fig. 4;

In Fig. 4 the controller is shown as connected with the other parts ofthe apparatus with which it cooperates. The armature of the generator isindicated at 27, and the main field-winding at 28, which is ashuntwinding. This shunt-winding determines the polarity of thegenerator-field, but the generator is provided also with a serieswinding29 of comparatively few turns, which acts as an opposition-winding, thegenerator being thus differentially wound.

The generator is connected with a storage batteryl30 and with anytranslating-devices, such as electric-lights, energized thereby throughmain conductors 31 and 32. Assuming that the generator is started inoperation, and. that the brushes have the polarity indicated by the plusand minus signs in Fig. 4:, current flows, from the upper brush, throughwires 33 and 34:, to the shuntstorage-battery, to the main conductor 32,

and back to the negative brush.

During normal operation of the generator, therefore, the armature9 ismaintained in closed circuitposition, through the com- 'bined eflect ofthe series-winding 31 and the shunt-winding 22.

The shunt-winding 22 of the controller is constantly energized, so longas the generator is in operation but the flow of current through it issmall, owing to its high resistance.

The shunt field-winding 28 of the generator draws current from the wire33, and the current then flows through wires 35 and 36 to the fixedcontact 13 of the limiting-relay. The current then flows through thearmature 8 and a wire 38 to the main-conductor 32, and thence back tothe armature of the generator. During the operation of the generator,therefore, the shunt field-winding is constantly energized.

The resistance-winding 26 is shunted across the Wires and 32, so that itis in parallel with the conductive path through the wire 36, thearmature 8, and the wire 38. When the generator is running at moderatespeed the magnetic pull upon the armature 8 is not sufficient toovercome the spring 16, so that this latter path is closed, theresistance-winding 23 is inefl'ective, and the flow through the shuntfield-winding 28 is determined by the resistance of the latter. When thegenerator-speed exceeds a predetermined amount, however, the increasedflow of current through the series-winding 21. of the controllerincreases the magnetization of the core 5, so that the spring 16 isovercome,- and the armature 8 is drawn to open-circuit position. Now thepath for the current through the shunt field-winding is through theresistance-winding 26, which cuts down the flow of current through thefield-Windingand opposes the tendency of the generator to attain anexcessive electromotive force.

It is a well-known characteristic of generator-controlling instrumentsof the type in question, that through a certain range of speed of thegenerator, which may be described as the critical speed, the controllerhas a vibratory action. That is to say,

the armature is first*attracted, thus cutting resistance into serieswith the field-winding of the generator, but this results in animmediate reduction in the output of the generator which, in turn,reduces the magnetization of the core of the, controller, whereupon thearmature is drawn back by its spring so as again to close the contactsby which the resistance is short-circuited. Thereupon the output of thegenerator immediately rises again, causing a repetition of the foregoingoperations. This action is usually very rapid, and the fluctuationsinthe output of the generator are more or less reduced or smoothed outby the impedance of the windings through which the current flows. 'Anunduly rapid vibration tends, however, to cause an amount of arcingbetween the contact-points which rapidly destroys them. The utility ofthe annular conductive-member or spool 25 of the present instrumentresides in the fact that it affords a path of low resistance foreddycurrents, which tend to delay flux-changes in the magnetic circuit,thus lengthening the period of the vibrations of the armature at thecritical speed of the generator. It is not necessary or practicable,however, to completely eliminate the vibratory action, and accordinglythe heat-conducting means mounted on the armature, as previouslydescribed, have utility in preventing overheating in consequence of thearcing due to the comparatively slow vibration to whlch 1t 1s stillsubject.

. Both the series-winding 21 and the shuntwinding 22 of the controllercooperate to produce the described action of the limitingrelay armature8, but the shunt-winding 22 is employed particularly in view of theoperation of the instrument as a master-relay. In case thegenerator-speed is reduced to such an extent that the electromotiveforce of the generator is not sufficient to produce a substantial flowof current through the series-winding 21 of the controller, the spring19 pulls the master-relay armature 9 away from the core 5, thus breakingthe connection between the generator and the storage-battery, andpreventing current from flowing back from the battery through thegenerator and being thus wasted. However, the shunt-winding 22 of thecontroller continues to be energized, so long as the generator has anymovement, and when the speed of the generator rises again to a properpoint the flow through the shuntwinding becomes suflicient to energizethe core 5 to a degree which will. permit the armature 9 to be drawnback, so as to close the main circuit and permit the generator to againsupply current for recharging the battery, or for energizing thetranslating-devices.

It will be apparent that the magnetic circuit of the controller embracesthe core 5, the armatures 8 and 9, and the iron baseplate 7.Accordingly, this magnetic circuit has two air-gaps, between therespective armatures and the ends of the core 5, and the reluctance ofthis magnetic circuit varies according as these air-gaps are opened orclosed. In consequence of this arrangement there is a useful cooperationbetween the two armatures 8 and 9. When the generator is running at highspeed the approach of the armature 8 to the core 5 reduces thereluctance of the magnetic circuit, thus increasing the pull of the coreupon the armature 9. and maintaining the contacts 17 and 18 infirmengagement with each other. On the other hand, as the generator-speedfalls the armature 8, in moving away from the core, increases-thereluctance of the magnetic circuit and diminishes the pull upon thearmature 9, thus preparing the instrument to perform the function, uponthe further reduction of the generator speed, of breaking the maincircuit. Finally, when the armature 9 moves away from the core thereluctance of the magnetic circuit is further increased, whereby thepull upon the armature 8 is diminished, thus permitting the latter,through theactionof the spr ng 16, to maintaimthe contact-points 12 and13 firmly in engagement until the speed of the generator again rises.Accordingly, the controller is sensitive at the critical speeds of thegenerator, while its contacts are maintained firmly closed at otherspeeds.

While the several novel features of the armatures.

magnetic core;

present invention whic have been pointed out are preferably employed inconjunction, to produce a simple, compact and reliable instrumentcapable of performing all of the functions of an automatic controller,it'will 1. In an electro-magnetic controller, a'

single magnetic circuit comprising two armatures; contacts controlled bythe armatures; and two windings, of high and low resistance,respectively, for energizing said circuit, the low-resistance windingbeing connected in series with the contacts controlled by one of thearmatures.

2. In an electro magnetic controller, a

a master-relay armature cooperating with one end of the core; alimiting-relay armature cooperating with the opposite end of the core;contacts controlled by the armatures; a magnetic connecting memberbetween the armatures whereby a magnetic circuit is formed through saidmember', the armatures, and the core; and a winding, on the core,aifecting the action of both 3. In an electro-magnetic controller, amagnetic core, an armature cooperating therewith; a spring tending tomove the armature away from the core; contacts-controlled by thearmature and arranged to be in engagement with eachvother when thearmature is away from the core; a magnetic winding upon the core; and anon-inductive resistance-winding also upon the core and connected inseries with said contacts.

4. Inv an electro-magnetic controller, a magnetic core, an armaturecooperating therewith; a spring tending to move the armature away fromthe core; contacts controlled by the armature and'arranged to be inengagement with each other when the armature is away from the core; amagnetic winding upon'the core; a non-inductive resistance-winding alsoupon the 'core and connected in series with said contacts-and a spool ofconductive material upon which the resistance-winding is wound and whichhas exposed flanges whereby the spool is adapted to perform the combinedfunctions of a heat-conductor and a path for eddy r currents. '60

5. -In an eleotro-magnetic controller, a magnet c core; a master-relayarmature and a l1m1t1ng-relayarmature cooperating with the core; springstendingv to move the armaby the limiting-relay armature.

' nected in series with the contacts controlled 6. In anelectro-magnetic controller, a

magnetic core; a master-relay, armature and a limiting-relay armaturecooperating with the core; springs tendingto move the armatures awayfromthe core; contacts controlled by the master-relay armature andarranged to be out of engagement with each other when said armature isaway from the core; contacts controlled by the limitingrelay armatureand arranged to be in engagement with each other when said armature isaway from the core; a winding, of comparatively low resistance,-upon thecore and connected in series with the contacts controlled bythe-master-relayarmature; a non-inductive resistance-winding, also uponthe core, connected in series with the contacts controlled by thelimiting-relay armature, and an inductive winding, upon the core, ofcomparatively high resistance and independent of thecontacts.

-7. In an electro-magnetic controller, a magnetic core provided with alow-resistance winding; an armature cooperating with the core; meanstending to draw the armature away from the core; contacts controlled bythe armature and arranged to be in engagement with each other when thearmature is away from the tacts being carried by plate, of highheat-conductivity, mounted on the armature, engaging the contact'carriedthereby, and extending away therefrom to conduct heat from saidcontact.-

8. In an electro-magnetic controller, a magnetic core; an armaturecooperating EDWARDA. Humane, D. Gunman.

core, one of said con-' the armature; and a

